The U.S. Food and Drug Administration on Tuesday approved a new treatment developed by Protalix BioTherapeutics Inc. (PLX, PLX.TV) for adults with a type of Gaucher disease, a rare genetic disorder.

The treatment, taliglucerase alfa, will be sold in the U.S. under the brand name Elelyso by Pfizer Inc. (>> Pfizer Inc.).

Pfizer also will sell the drug in most places outside the U.S. The drug, which is the first plant-derived cell-based enzyme replacement, replaces an enzyme called glucocerebrosidase in people with type 1 Gaucher disease. Elelyso is produced using genetically engineered carrot cells.

People with Gaucher disease lack glucocerebrosidase, which causes an accumulation of a fatty substance inside cells. The fatty accumulation can lead to enlargement and malfunctioning of the liver, spleen, bone marrow and occasionally, the lung, kidney, and intestine. About 6,000 people in the U.S. have type 1 Gaucher disease, according to the FDA.

Pfizer and Protalix have already been making Elelyso available to some Gaucher disease patients as part of an early access program because of manufacturing issues at Genzyme, a unit of Sanofi SA (SNY, SAN.FR), which makes another glucocerebrosidase-enzyme replacement product, Cerezyme. Earlier this year, Genzyme said the manufacturing problems had been fixed and that the company is able to make enough of the product to supply current patients in the U.S.

Shire PLC (SHPGY, SHP.LN), which also makes a Gaucher disease treatment, Vpriv, has said inventories of the product will be "below target levels" until the FDA signs off on a second manufacturing plant in the U.S. However, the company also said it has the capacity to meet anticipated demand for Vpriv. Cerezyme and Vpriv are approved for use in children as well as adults.

Officials from Pfizer and Protalix said the companies have already built enough inventory of Elelyso to supply to patients for at least 24 months.

Elelyso is an infusion that is administered by health-care professionals every other week.

The FDA said the approval of Elelyso was based on two studies involving 56 patients with type 1 Gaucher disease. One study looked at 31 patients who had not previously received enzyme-replacement therapy. The study showed Elelyso reduced the size of patients' spleens by an average of 29% to 40%, depending on the dose of the drug, after nine months of treatment. The other study involved 25 patients who were switched from Cerezyme. The FDA said that study showed Elelyso was effective in maintaining spleen and liver volumes, blood platelet counts and hemoglobin levels during a nine-month evaluation period.

The agency said the most common side effects were infusion reactions and allergic reactions.